Band gap tuning in nanocomposite ZrO2-SnO2 thin film achieved through sol-gel co-deposition method

Transparent SnO2, nanocomposite ZrO2-SnO2 and ZrO2 thin films were prepared by sol-gel dip-coating technique. X-ray diffraction (XRD) spectra showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. X-ray photoelectron spectroscopy (XPS) gave Zr 3d, Sn 3d and O 1s spectra of the nanocomposite ZrO2-SnO2 thin film which revealed the presence of oxygen vacancies in the nanocomposite ZrO2-SnO2 thin film. Scanning electron microscopy (SEM) observations showed that microstructure of the nanocomposite ZrO2-SnO2 thin film consists of uniform dispersion of isolated SnO2 particles in ZrO2 matrix. The band gap for the ZrO2 was estimated to be 5.51 eV and that for the nanocomposite ZrO2-SnO2 film was 4.9 eV. These films demonstrated the tailoring of band gap values which can be directly employed in tuning the band gap by simply changing the relative concentration of zirconium and tin elements. Photoluminescence (PL) spectra revealed an intense emission peak at 424 nm in the nanocomposite ZrO2-SnO2 film which indicate the presence of oxygen vacancies in ZrSnO4.